A short message service provides a method for delivering a short message between mobile terminals and is widely used in a circuit switched (CS) network.
The 3rd Generation Partnership Project (3GPP) R5 stage introduces an Internet Protocol (IP) multimedia subsystem (IMS), in which: a Session Initiation Protocol (SIP) is introduced to perform business control based on a packet domain of an existing mobile communication network, and a unified platform is provided for providing various multimedia services through separating between the business control and an underlying bearer network.
At present, 3GPP has proposed a network architecture for interworking a traditional short message service and an IP short message service based on the IMS as shown in FIG. 1, which includes a Short Message Service Centre (SMC), an SMS-Gateway MSC (SMS-GMSC), an IP-Short-Message-Gateway (IP-SM-GW) and a Home Location Register/Home Subscriber Server (HLR/HSS).
The SMC, i.e., SME-SC, is responsible for relaying, storing or forwarding a short message.
The SMS-GMSC receives the short message from the SMC, queries a routing message from the HLR, and routes the short message to a Mobile Switching Centre (MSC) where a receiver is located according to the query result.
The IP-SM-GW provides an internetwork short message interworking function between a User Equipment (UE) and a Global System for a Mobile Communications (GSM)/a Universal Mobile Telecommunications System (UMTS).
The HLR/HSS provides a routing query function for short message service. The HLR/HSS may return an address of the IP-SM-GW in a query routing response message if the address of the IP-SM-GW is registered by a UE, when the SMS-GMSC queries routing information.
For a network containing the IMS, a short message mobile termination (SMS-MT) flow of a UE is given in 3GPP 23.204 specification, as shown in FIG. 2, which includes the steps 1 to 6.
In step 1, an address of the IP-SM-GW is statically stored in the HLR/HSS to provide a support for SMS OVER IP. Or the called UE performs an IMS registration process, such that, a third party registration process from the IP-SM-GW to HLR/HSS is triggered according to trigger criteria by means of a Serving-Call Server Control Function (S-CSCF) and the address of the IP-SM-GW is stored in the HLR/HSS dynamically. The called UE performs an IMS de-registration process, such that, a de-registration process from the IP-SM-GW to the HLR/HSS is triggered, and the dynamically stored address of the IP-SM-GW is deleted from the HLR/HSS.
In step 2, the SMC sends a short message to the SMS-GMSC.
In step 3, the SMS-GMSC sends a route query request to the HLR/HSS and the HLR/HSS forwards the route query request to the IP-SM-GW according to the pre-registered IP-SM-GW address. The IP-SM-GW sends a route query request to HLR/HSS once again, the HLR/HSS returns information about network registered by the UE, including the MSC and a Serving GPRS Support Node (SGSN) if the query comes from IP-SM-GW. The IP-SM-GW returns its address to the SMS-GMSC, after receiving a response message returned by the HLR/HSS.
In step 4, the SMS-GMSC sends the short message to the IP-SM-GW according to the received address of the IP-SM-GW returned by the IP-SM-GW.
In step 5, The IP-SM-GW determines and selects an IMS domain according to the network information registered by the UE, converts a Mobile Subscriber ISDN Number (MSISDN) into a Telephony Resource Locator (TELURL), and finds an S-CSCF where the called UE is located.
In step 6, IP-SM-GW delivers the short messages to the S-CSCF in the IP domain.
As can be seen from the above procedure, once the HLR/HSS in the mobile network receives a terminating short message routing query from the mobile network SMC, the HLR/HSS firstly transfer the short message routing query of the called UE to the IP-SM-GW, regardless of the receiver is currently registered in the mobile CS network or the LTE/IMS network. the IP-SM-GW selects a delivery domain according to network information (addresses of MSC, SGSN, IP-SM-GW address) registered by the UE, which is returned by the HLR/HSS, after the IP-SM-GW re-performs the terminating short message routing query from the HLR/HSS.
Actually, Long Term Evolution (LTE) terminals may also have a circuit switched fallback (CSFB) registration capability. Therefore, when the UE resides in the LTE network, the UE may implement a dual registration in both the mobile CS network and the LTE/IMS network. In this case, a short message for a CSFB UE can either be delivered via the IMS domain or the CS domain.
Due to a limited coverage of the LTE network during the initial deployment of the LTE network, when a UE switches to the CS network from the LTE network, a registration status of the UE in the LTE/IMS network is not cancelled, which resulting in the presence of a fraudulent LTE/IMS registration status of the UE in the network.
The above SMS OVER IP process of 3GPP23.204 specification have following drawbacks: when fraudulent IMS registration of a UE occurs, a short message routing of the called UE of the short message service centre is uniformly forwarded to the IP-SM-GW, whereas the original routing manner in which the SMS-GMSC performs a short message delivery in the CS domain cannot be used any more. Further, when the IMS domain is selected by the IP-SM-GW, the delivery process may fail, and then it is necessary for the IP-SM-GW to retry message delivery in the CS domain again, thereby prolonging short message delivery time, and wasting network signaling resources.
Therefore, more efficient short message routing solutions needs to be provided for resolving the above problems, so as to provide a better experience of diversified short message services with high quality in the LTE/IMS network for users.